[all-commits] [llvm/llvm-project] 39e602: [InstCombine] try to fold binop with phi operands

[Sanjay Patel via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 39e602b6c4335b2572c74eaf9a666bebde7fd8b5
      https://github.com/llvm/llvm-project/commit/39e602b6c4335b2572c74eaf9a666bebde7fd8b5
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2022-01-22 (Sat, 22 Jan 2022)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
    M llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
    M llvm/lib/Transforms/InstCombine/InstCombineInternal.h
    M llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
    M llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
    M llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
    M llvm/test/Transforms/InstCombine/binop-phi-operands.ll
    M llvm/test/Transforms/InstCombine/zext-or-icmp.ll

  Log Message:
  -----------
  [InstCombine] try to fold binop with phi operands

This is an alternate version of D115914 that handles/tests all binary opcodes.

I suspect that we don't see these patterns too often because -simplifycfg
would convert the minimal cases into selects rather than leave them in phi form
(note: instcombine has logic holes for combining the select patterns too though,
so that's another potential patch).

We only create a new binop in a predecessor that unconditionally branches to
the final block.
https://alive2.llvm.org/ce/z/C57M2F
https://alive2.llvm.org/ce/z/WHwAoU (not safe to speculate an sdiv for example)
https://alive2.llvm.org/ce/z/rdVUvW (but it is ok on this path)

Differential Revision: https://reviews.llvm.org/D117110